"With the threat of Neolution having carte blanche access to clone biology, Sarah is desperate to gain control, but realises she must change tactics to pursue a long game," the synopsis reads.

"Protecting both her families, and the host of clones she's yet to meet, Sarah and those still fighting the fight will uncover the missing pieces of the insidious conspiracy – and finally learn the story behind their origin."

"Four seasons on Orphan Black, we chew up a lot of story every season," series co-creator Graeme Manson explained. "We chew up a couple of seasons' worth of story every season. It's a fast-paced show.

"I think we've done a good job of keeping the show sharp and relevant with packing all that much stuff in, and our biggest fear is repeating ourselves. We just didn't want the show to become watered down."

Orphan Black will air its final season on BBC America in the US on June 10, while the show streams on Netflix in the UK.